The present invention pertains to a self-locking sling for loading, unloading and transporting goods packed into bags or the like.
Since several years, slings are used which are constituted by a strap, thong or ribbon successively folded and bent so as to constitute a central carrying zone surrounded by a number of loops. Such slings have the shape of a three or four bladed clover-leaf.
The load, for instance a pile of filled bags, is placed on said carrying zone whereafter the loops are brought upwards around the load and are mutually connected by means of a twine. The free extremities of the loops are intended to be engaged by the hook of a crane, for instance when the load must be heaved in or out of the hold of a ship. Such a known sling holds the load together only when the latter is suspended. In other circumstances, the sling remains around the load without acting on the latter. It is therefore generally impossible to manipulate the load with other devices than a crane, for instance with a fork lift.
This is often a great disadvantage, for instance when the merchandise must be successively transported by different carrying means.
It has therefor already been proposed to use a sling system constituted by a bottom supporting sling and a top hoisting sling these two components being secured together by means allowing a relative motion between the components in one direction and restricting or preventing movement in the other direction (GB No. 1.394.823). The purpose of this known system is to obtain a self tightening effect on the load when the latter is hoisted and a locking of the system after tightening. To this end, aforesaid means consist of pairs of chain links attached to suitable parts of the bottom supporting sling. This is an expensive solution, as the slings are generally used only once (one-way). Furthermore, interconnecting said components in this fashion when building up load units is time consuming. Therefor, it has been suggested (GB No. 1.394.823) to dispense with said chain links and to simply pass loops of the top sling through loops of the bottom sling. While this allows to maintain the self-tightening feature of the system, the eminently desirable self-locking characteristic is lost.